3. WHAT IS STEGANOGRAPHY
The word steganography literally means covered writing as derived from
Greek. Steganography is the art of concealing the existence of information
within seemingly innocuous carriers. In broad sense, term Steganography is
used for hiding message within an image.
Steganography is the art and science of communicating in a way which
hides the existence of the communication. In contrast to cryptography, where
the "enemy" is allowed to detect, intercept and modify messages without
being able to violate certain security premises guaranteed by a cryptosystem,
the goal of steganography is to hide messages inside other "harmless"
messages in a way that does not allow any "enemy" to even detect that there is
a second secret message present. Steganography is in the (especially military)
literature also referred to as transmission security or short TRANSEC.
4. STEGANOGRAPHY VS CRYPTOGRAPHY
Steganography can be viewed as akin to cryptography. Both have been used
throughout recorded history as means to protect information. At times these
two technologies seem to converge while the objectives of the two differ.
Cryptographic techniques "scramble" messages so if intercepted, the
messages cannot be understood. Steganography, an essence, "camouflages" a
message to hide its existence and make it seem "invisible" thus concealing the
fact that a message is being sent altogether. An encrypted message may draw
suspicion while an invisible message will not.
Steganography cannot be detected. Therefore, it is used when encryption is
not permitted. Or, more commonly, steganography is used to supplement
encryption. An encrypted file may still hide information using steganography,
so even if the encrypted file is deciphered, the hidden message is not seen.
5. EVOLUTION OF STEGANOGRAPHY
•CODE BREAKERS : David Kahn's The Code breakers and Bruce Norman’s
Secret Warfare: The Battle of Codes and Ciphers recounts numerous tales of
steganography .
•INVISIBLE INK : An innocent letter may contain a very different message
written between the lines with invisible ink. Common sources for invisible inks
are milk, vinegar, fruit juices and urine. All of these darken when heated. Later
on, more sophisticated inks were developed which react to various chemicals.
•MICRODOTS: The Germans developed microdot technology. Microdots are
photographs the size of a printed period having the clarity of standard-sized
typewritten pages. The first microdots were discovered masquerading as a period
on a typed envelope carried by a German agent in 1941. The message was not
hidden, nor encrypted. It was just so small as to not draw attention to itself (for a
while). Besides being so small, microdots permitted the transmission of large
amounts of data including drawings and photographs
6. TYPES OF STEGANOGRAPHY
MESSAGES IN TEXT program is called SPAM
MIMIC.
MESSAGES IN STILL IMAGES most popular tool is
outguess.
MESSAGES IN AUDIO data is hidden in layer III of
encoding process of MP3 file. Messages in audio are
always sent along with ambient noise.
MESSAGES IN VIDEO embedding information into
multimedia data has gained increasing attention lately.
7. AN EXAMPLE
Fishing freshwater bends and saltwater coasts rewards anyone feeling
stressed. Resourceful anglers usually find masterful leapers fun and admit
swordfish rank overwhelming anyday.
“Send lawyers guns and money”
•Most communication channels like telephone lines and radio broadcasts
transmit signals which are always accompanied by some kind of noise. This
noise can be replaced by a secret signal that has been transformed into a
form that is indistinguishable from noise without knowledge of a secret key
and this way, the secret signal can be transmitted undetectable.
8. DISSECTING STEGANOGRAPHY
Steganography is a term used for hiding messages within an image.
Any color pixel is made of a combination of red –green-blue
mode(RGB) wherein each RGB component consist of 8 bits. If letters
in ASCII are to be represented within the color pixels, the rightmost
digit, called the least significant bit (LSB), can be altered.
Any variation in the value of this bit leads to very minimal
variation in color. If we have to hide the word ‘digit’ in the image, we
take the LSB of every color and hide each bit of the word in its RGB
combination.
To insert the letter ‘D’ we modify three color pixels with three bits
in each color pixel, we utilize 14 color pixels to hide the entire word
with only 1 bit in the 14th pixel.
CONTD…………..
9. 00000000 11111111 10101010 ASCII CHARACTER CODE
01010100 01010100 10101010
D-01000100
01010100 01010100 I-
01101001
G-01100111
I-01101001
T-01110100
MSB
AMOUNT OF DATA STORED INSIDE A PICTURE
DISSECTING STEGANOGRAPHY……..
10. Suppose we have a 24-bit image 1024 x 768 (this is a common
resolution for satellite images, electronic astral photographs and other
high resolution graphics). This may produce a file over 2 megabytes in
size (1024x768x24/8 = 2,359,296 bits). All color variations are
derived from three primary colors, Red, Green and Blue. Each primary
color is represented by 1 byte (8 bits). 24-bit images use 3 bytes per
pixel. If information is stored in the least significant bit (LSB) of each
byte, 3 bits can be a stored in each pixel. The "container" image will
look identical to the human eye, even if viewing the picture side by
side with the original.
DISSECTING STEGANOGRAPHY……..
11. STEPS FOR HIDING AN IMAGE
USING STEGANOGRAPHY
Start s-tool and window explorer using the later as drag and drop interface
the software.
Drag and drop the image to be used as the carrier file from the explorer onto
the actions window in s-tool.
Drag and drop the data file on the carrier file.
Give pass phrase and encryption algorithm when prompted. Pass these to
receiver too.
The hidden file is ready. Receiver has to click on the “reveal” button to
extract the data.
12. DIGITAL WATERMARKING
Usually carrier file carry hidden data unrelated to the
content in which it is embedded, but digital
watermarking holds information about its carrier
medium.
Information such as a number or a text into a
multimedia file can be added to carrier file through
slight data modification. this process has gained huge
acclaim from the media for enabling copyright for their
products.
Video steganography is more suited to avoiding piracy
and is mostly used for digital watermarking.
13. Types of digital watermarking
ROBUST DIGITAL WATERMARKING A robust watermark is
embedded in the file in such a way that even if the file is later
transformed, the watermark will not be removed
FRAGILE DIGITAL WATERMARKING is similar to fragile
analog watermarks-if the data is altered or copied in exactly, the
watermark is corrupted
For ensuring the integrity of data, digital signatures are
preferred but fragile digital watermarking can detect data tempering
without alerting the culprit. Compatible players refuse to play content
that does not bear a valid watermark.
14. WHAT IS “STEGANALYSIS”
The art of detecting, decoding and altering messages
hidden via steganography is called steganalysis. It is
easiest when before as well as after steganography
copies of file are present.
Steganalysis can make the hidden data work against
the creator. Any malicious interceptor could alter as
carrier file without the knowledge of sender or the
intended receiver. Hence inaccurate or wrong data could
be passed under identity of the original sender.
15. SOME OUTSTANDING
FACTS
1. steganos security suite 4 uses powerful 128-bit encryption. It would take 1
billion powerful computers million of years to try every combination to gain
access to your personal information. this software uses steganography along
with encryption to completely secure your data.
2. Blindside is an application of steganography that allows you to conceal a
single file or set of files within a standard computer image. The new image
looks identical to the original, but can contain up to 50k of data. The hidden
files can also be password encrypted to prevent unauthorized access.
3. Mp3stego hides information in mp3 files during the compression process.
The data is first compressed, encrypted and then hidden in the mp3 bit stream.
Although mp3stego was written with steganographic applications in mind, it
can also be used as a copyright marking system for mp3 files.
16. ADVANTAGES OF
STEGANOGRAPHY
It can be used for safeguarding data,
such as in the field of media where
copywriting ensures authenticity.
It can be used by intelligence agencies for
sending their secret data.
